Viveka Herzum


In this photo, the main physics principles shown are air pressure, surface tension, and interference phenomena, which have to do with light waves. The air molecules inside the bubble itself exert internal pressure, while outside the bubble atmospheric pressure counteracts this inner pressure. The bubble itself is composed of a mixture of soap and water. However, within the soap mixture, the soap molecules are lighter than the water molecules. For this reason, once the bubble is formed, the force of gravity pulls the water towards the bottom of the bubble while the soap is pushed to the top.

Since water has a higher surface tension than soap due to its high polarity, the mass of the bubble will be unevenly distributed; the top of the bubble will gradually become thinner and therefore weaker and it will eventually burst. Surface tension is also responsible for the form of the bubble. Molecules of water tend to form a shape that minimizes the tension on the surface, which, due to the effects of cohesion, creates a rounded/spherical shape. The bubble in the photo follows this principle., maintaining a mostly rounded shape. The rainbow of colors seen on the iridescent surface of the bubble is caused by the interference of light reflecting off the front and the back surfaces of the bubble, comprised of a thin soap and water film. The waves of different frequencies create different color patterns, with blue having the highest frequency and red having the lowest.

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